This article evaluates the use of Priority Queueing models to
achieve delay differentiation in IP networks operating under
the Class of Services paradigm. Three models are considered:
proportional model, additive model and a novel hybrid schema
based on the upper time limit model. The characteristics,
behaviour and viability of these models are analysed as regards
traffic delay differentiation. The impact of each model on
traffic aggregation and on individual flows is also evaluated.
This study is complemented by the analysis of delay
differentiation from an end-to-end perspective. An adaptive
differentiation mechanism is also proposed and discussed.